The European Union has put sanctions on senior officials from the Russian military intelligence agency, the GRU, over the Salisbury poisonings.

Four people have been sanctioned - including the head of the GRU, deputy head, and two agents who are believed to have carried out the attack.

The Novichok nerve agent they used severely poisoned three people and killed a fourth, Dawn Sturgess.

The sanctions put a ban on travel to the EU and freezes any assets there.

They also prevent any person or company in the EU from providing any financial support to those affected.

This is the first time the EU has used its new powers to sanction those connected to chemical weapons manufacture and use, which it created in October last year.

All four GRU staff remain in Russia, which will not extradite them to face charges.

In a statement, the EU said:

Anatoliy Vladimirovich Chepiga and Alexander Mishkin "possessed, transported and then, during the weekend of 4 March 2018, in Salisbury, used a toxic nerve agent" for which the UK has charged them with attempted murder

Igor Olegovich Kostyukov, head of the GRU, and Vladimir Stepanovich Alexseyev, the deputy head, are both accused, "given his senior leadership role" to be "responsible for the possession, transport and use" of the nerve agent

The intended target of the attack, Sergei Skripal, survived despite being severely poisoned, as did his daughter Yulia. Their whereabouts are kept secret.

But months after the initial poisoning, a resident of nearby Amesbury, Dawn Sturgess, died of Novichok poisoning. Her partner, Charlie Rowley, had found a bottle in a perfume box and had given it to her.

It contained the nerve agent, apparently discarded after the attack on the Skripals. Mr Rowley was also poisoned, but survived.

The sanctioning of the two agents comes after months of insistence from Moscow that there is no evidence to show their guilt.

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Media captionOn the trail of Russians Alexander Petrov and Ruslan Boshirov, who UK police believe carried out a nerve agent attack in Salisbury in March 2018

In the aftermath of the poisoning, UK police released the names and photographs of Mr Chepiga and Mr Mishkin, who had used the pseudonyms Ruslan Boshirov and Alexander Petrov, having traced their steps meticulously through CCTV footage.

Despite the presence of the two Russian intelligence agents in Salisbury at the time and the use of a nerve agent believed to have been made in Russia, Moscow insisted the men were innocent.

In an interview on state-run television channel RT, the pair said they were merely tourists, denied having travelled under fake names, and said they had made the journey to see the city's cathedral. The appearance was widely ridiculed and the story labelled implausible.

After the EU announced its sanctions, Russia's foreign ministry threatened retaliation "against this unfriendly action".

It said the sanctions were adopted under the "pretext" that the pair were involved in the Salisbury attack, but maintained that the accusations against them "do not stand up to scrutiny".

"The information campaign unleashed by the British authorities on this case pursues, first of all, domestic political goals," it said, highlighting the current "crisis" over Brexit.

It also accused the EU of circumventing the United Nations Security Council and taking unilateral action.

Alongside the Russian GRU agents, five people from a Syrian institute widely held responsible for damaging chemical weapons, the Scientific Studies and Research Centre, were also hit with the same sanctions.